1. Field of the Invention
The present invention relates to a technique of detecting a dropout in a disk drive which reproduces data recorded on a recording disk.
2. Description of the Related Art
As a technique of detecting a dropout, i.e., a phenomenon in which a signal cannot be favorably read due to such factors as damage on a recording disk, in a disk drive which reproduces data recorded on the recording disk, there is known a technique of detecting the occurrence of the dropout on the basis of an envelope of an RF (Radio Frequency) signal read from an optical disk by a pickup (e.g., Japanese Unexamined Patent Application Publication No. 2003-132533). According to the technique, when the envelope of the RF signal rapidly decreases by a predetermined level or more, a dropout detection signal indicating the occurrence of the dropout is output during the decrease of the envelope.
According to the technique described in this publication, a change in the amplitude magnitude of the envelope of the RF signal causes a change in the timing and the duration of the output of the dropout detection signal indicating the occurrence of the dropout. As a result, a process in response to the occurrence of the dropout cannot be performed with a similar characteristic. The amplitude of the envelope refers to the difference between the magnitude of the envelope immediately before and immediately after the occurrence of the dropout and the magnitude of the envelope during the occurrence of the dropout.